1. Field of the Invention
This invention relates to displacement chromatography. More particularly, this invention relates to a process for separating a known material from a mixture of materials using displacement chromatography.
2. Description of the Related Art
In the practice of displacement chromatography, a mixture of several materials, dissolved in a carrier, are loaded onto a stationary phase material in a chromatography column. Then a displacement agent, comprising a material capable of being more strongly bound to the stationary phase material than the particular material of interest in the mixture, and usually capable of being more strongly bound than any of the other materials in the mixture, is fed through the column to displace the already bound materials, with the most weakly bound material coming off the column first by being displaced by the next most weakly bound material.
The feasibility of this separation method has been demonstrated using known mixtures of materials, wherein a displacement agent may be selected which is more strongly bound to the stationary phase than any of the other materials, by virtue of being able to intelligently select such a displacement agent based on the prior knowledge of the other materials in the mixture. However, problems arose in the past when this separation technique was applied by others to a situation wherein a known material was to be separated from an unknown mixture, i.e., a mixture which might contain unknown materials. In such a situation, it was difficult, and sometimes impossible, to preselect a displacement agent capable of displacing all of the materials in the mixture, when that mixture did contain unknow materials, and in particular when some of such unknown materials were more strongly bounded to the stationary phase than the displacement agent selected.
I believe that the principal reason why displacement chromatography has never achieved commercial success is the failure of others to recognize the importance of the presence of these unknown materials in commercial solutions or materials, as opposed to artificial or model laboratory preparations.
Even when all of the components in the mixture are known, but some are substantially more strongly held than the desired component, it has become accepted by those skilled in the art that to satisfactorily practice displacement chromatography, one must use a displacement agent capable of being more strongly bound to the stationary phase than any of the materials in the mixture to be separated.
However, this can diminish the value of displacement chromatography as a separation tool for many mixtures, because one must first conduct tests to determine the most strongly bound material in the mixture, then determine whether or not a stronger displacement agent is available, and then determine the economics of using such a strong displacement agent.
It has also been found that in practical commercial mixtures, there are present components in small concentrations which frequently elude analysis, but are more strongly bound to the stationary phase than the displacement agent selected to be more strongly bound than the components which could be found by the analysis. The presence of this small concentration of materials more strongly bound than the selected displacement agent prevents or interferes with successful displacement chromatography.
It would, therefore, be desirable to provide a process for practicing displacement chromatography without requiring the use of a displacing agent more strongly bound to the stationary phase than any component in a feed mixture.